Field of the Disclosure
The present disclosure generally relates to a fixed cutter drill bit having core receptacle with concave core cutter.
Description of the Related Art
U.S. Pat. No. 5,655,614 discloses a self-centering drill bit including a head portion having a plurality of polycrystalline diamond compact cutting elements arranged in blades that extend outwardly away from a surface of the bit. A cavity is centrally located on the head portion and is formed between adjacent blade ends. The cavity includes wall portions defined by the blade end portions. The cavity serves to house a core portion that is formed during drilling operation of the bit. The head portion is balanced to form and transmit a force from a designated wall portion to the core portion within the cavity. At least the designated wall portion includes a low friction abrasion resistant surface. The cavity includes a rigid element extending outwardly away from the head portion to reduce the core within the cavity upon contact. The force transmitted to the core portion causes a countering force to be imposed by the core to the wall portion that keeps the bit aligned with its rotational axis and, thus prevents whirling.
U.S. Pat. No. 8,820,441 discloses a drill bit having fixed Polycrystalline Diamond Compact cutters and used to drill a borehole having a core stump therein. A plurality of additional fixed Polycrystalline Diamond Compact cutters are disposed in the dome of the bit and are usable to concentrate stresses in the top end of the core stump to facilitate the cutting down of the core stump.
U.S. Pat. No. 8,839,886 discloses a drill bit configured for boring holes or wells into the earth and including a plurality of blades configured with a recessed center such that the blades cut a core therebetween. Cutting elements in the recessed center are configured to cut and remove the core. The recessed center has a first diameter at a height from the cutting elements in the recessed center and a second diameter smaller than the first diameter such that the confining stress on the core is relieved prior to being cut by the cutting elements in the recessed center.
U.S. Pat. No. 8,960,335 discloses a bit for drilling wells and having a front face with radial blades having cutting elements distributed around the front face. A space for forming a core is situated at the center of the front face. A cavity is provided for evacuating the core towards a periphery of the bit. At least a portion of the cavity is situated between adjacent blades. The cavity is delimited by two lateral surfaces and a clearance surface set back with respect to the front face, and the cavity is open in a direction opposite the clearance surface. The bit may be used in methods for drilling wells and makes it possible to rapidly drill wells of great depth in all types of rock without the risk of clogging.
U.S. Pat. No. 7,392,857 discloses a drill bit including an axis of rotation, a body, and a working face. The body includes a fluid passageway with a first seat and houses a jack element substantially coaxial with the axis. A stop element is disposed within the passageway and has a first near-sealing surface. The jack element has a shaft intermediate an indenting end and a valve portion. The valve portion has a second near-sealing surface disposed adjacent the first near-sealing surface and a second seat disposed adjacent the first seat. As a formation strongly resists the jack element, the distance between the sealing surfaces narrows. This causes an increase in fluid pressure within the passageway and forces the indenting end down into the formation. This movement of the jack element relieves the pressure build up such that the formation pushes the jack element back, thereby oscillating the jack element.
U.S. Pat. No. 7,591,327 discloses a method for drilling a bore hole including the steps of deploying a drill bit attached to a drill string in a well bore, the drill bit having an axial jack element with a distal end protruding beyond a working face of the drill bit; engaging the distal end of the jack element against the formation such that the formation applies a reaction force on the jack element while the drill string rotates; and applying a force on the jack element that opposes the reaction force such that the jack element vibrates and imposes a resonant frequency into the formation.
U.S. Pat. No. 7,641,002 discloses a rotary drag drill bit having a body intermediate a shank and a working face. The working face has a plurality of blades converging towards a center of the working face and diverging towards a gauge of the working face. A carbide section is fixed to the working face and positioned within a pocket disposed within an inverted cone of the working face. The carbide section has a distal end exposed within the working face.
U.S. Pat. No. 7,694,756 discloses a drill bit having a bit body intermediate a working face and a shank end adapted for connection to a downhole drill string. The working face has at least three fixed blades converging towards a center of the working face and diverging towards a gauge of the bit, at least one blade having a cone region adjacent the center of the working face. The cone region increases in height away from the center of the working face and towards a nose portion of the at least one blade. An opening is formed in the working face at the center of the bit along an axis of the drill bit's rotation, the opening leading into a chamber with at least one wall. An indenting member is disposed within and extends from the opening, is substantially coaxial with the axis of rotation, and is fixed to the wall of the chamber.
U.S. Pat. No. 8,020,471 discloses a drill bit having a body intermediate a shank and a working face, the working face including a plurality of blades formed on the working face and extending outwardly from the bit body. Each blade includes at least one cutting element. The drill bit also has a jack element coaxial with an axis of rotation and extending out of an opening formed in the working face. A portion of the jack element is coated with a stop-off.
U.S. Pat. No. 8,820,440 discloses a steering assembly for downhole directional drilling including an outer bit having a bore and an outer cutting area and in inner bit having an inner cutting area and connected to a shaft that is disposed within the bore. At least one biasing mechanism is disposed around the shaft. At least one fluid channel is disposed within the outer bit and redirects fluid to the at least one biasing mechanism causing the at least one biasing mechanism to push the shaft and alter an axis of the inner bit with respect to an axis of the outer bit.
U.S. Pat. No. 8,130,117 discloses a downhole drill bit with a body intermediate a shank and a working surface. Extending from the work surface is a wear resistant electric transmitter electrically isolated from the drill bit body. A wear resistant electrically conductive receiver, also electrically isolated from the bit body, may be connected to a tool string component. The working surface may also have at least two wear resistant electrodes located intermediate the transmitter and receiver that are adapted to measure an electric potential in the formation.
U.S. Pat. No. 7,661,487 discloses a downhole percussive tool including an interior chamber and a piston element slidably sitting within the interior chamber forming two pressure chambers on either side. The piston element may slide back and forth within the interior chamber as drilling fluid is channeled into either pressure chamber. Input channels supply drilling fluid into the pressure chambers and exit orifices release that fluid from the same. An exhaust orifice allows additional drilling fluid to release from the interior chamber. The amount of pressure maintained in either pressure chamber may be controlled by the size of the exiting orifices and exhaust orifices. In various embodiments, the percussive tool may form a downhole jack hammer or vibrator tool.
U.S. Pat. No. 8,191,656 discloses a cutter configured with a diamond table made from a thin hard facing material layer of polycrystalline diamond bonded to a backing layer made from cemented tungsten carbide. The face of the diamond table includes a concavity formed with a curved shape wherein at least a portion of the face in a center of the cutter is recessed with respect to at least some portion of the face about the perimeter of the cutter. This concave curved shape is formed in the diamond table itself such that the diamond table has a varying thickness depending on the implemented concavity